In response to the expanding need for advanced live cell imaging capabilities, the University of Pennsylvania School of Veterinary Medicine (SOVM) established an Imaging Core facility in the summer of 2008. With the involvement of several pioneer labs, and with nearly $900,000 contributed by the University Provosts office and Departments and Centers in the SOVM, we purchased several microscopes including a Leica SP5 multiphoton system. Expanding utilization of the core has been greatly facilitated by the expertise of our core director, Dr. Bruce Freedman and the core manager, currently Dr. Gordon Ruthel. Both have been instrumental in the development of a range of new applications for our users. As a group we have an enormous amount of collective expertise, including multiphoton real-time imaging of pathogen infection and immune responses in the brain, intestine, skin, and secondary lymphoid organs, as well as the behavior of tumors within the tissue matrix. FRET/FLIM based approaches are used to track the localization, interactions, and activity of signaling molecules in response to receptor stimulation, photo-activation to generate signaling intermediates instantaneously in situ, and live imaging of calcium and mitochondrial function. Since its inception, the data generated in this core has contributed to multiple manuscripts and successful grant applications. The experimental needs of our user group continuously drives us to expand our capability and each of the hardware components requested in this proposal was chosen to address specific current and future needs of our active user base. The ultimate goal of this application is to modernize this instrument and capitalize on technological developments to enhance multiphoton imaging capability that have become available since its installation. Funds requested will be used for hardware upgrades that will 1) increase the overall capability including depth of imaging, acquisition speed/temporal resolution, spatial coverage, detection sensitivity, and excitation flexibility 2) replace a legacy computer system that controls the instrument and add off line streaming and analysis capability, and 3) provide robust environmental control for long-term real time imaging of living tissues and cells.